Pyroelectric vidicon camera tubes use pyroelectric targets as the image sensing elements. As disclosed in an article entitled "Theory and Characteristics of Pyroelectric Imaging Tubes" by B. Singer (appearing in a book entitled Advances in Image and Pick-up Display, Vol. 3, editor B. Kazan, Academic Press, 1977), a target is typically fabricated by cutting and polishing a pyroelectric crystal or ceramic into a cylindrical rod. The rod is then cut into slices which, after polishing, produce wafers of typically 30 .mu.m thickness.
It is often desirable to reduce the thickness of such a wafer even further than disclosed in the above article, U.S. Pat. No. 4,018,638 discloses a method of reducing the thickness of a wafer of pyroelectric material by etching a central region of the wafer to produce a thin membrane having a relatively strong outer rim. This process is known as "cup etching".
Although cup-etching produces pyroelectric targets having the desired thickness and strength, the etched surfaces of targets prepared by this method frequently show lines and patterns. It has been discovered that these lines and patterns may seriously degrade the image quality in vidicon tubes which incorporate pyroelectric targets manufactured according to the process of U.S. Pat. No. 4,018,638.